The present invention generally relates to rotary recording medium and reproducing apparatus therefor, and more particularly to a rotary recording medium and a reproducing apparatus therefor, with which a fine and stable still picture can be obtained during a still picture reproduction mode, and video and audio signals can be reproduced without introducing inconveniences during a normal reproduction mode.
An information signal recording and reproducing system has been previously proposed in which the recording system forms pits in accordance with the information signal to record the information signal along a spiral track on a flat rotary recording medium (hereinafter simply referred to as a disc), without forming a groove therein. In the reproducing system, a reproducing stylus traces over along this track to reproduce the recorded information signal in response to variations in the electrostatic capacitance formed between a reproducing stylus and the disc.
In this previously proposed system, since no grooves are provided on the disc for guiding the reproducing stylus, it becomes necessary to record pilot or reference signals on or in the vicinity of a track of the information signal such as a video signal, on the disc. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged, since the recording track has no groove. The reproducing stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow-motion, or quick-motion picture reproduction becomes possible.
In the above type of a disc, a standard is set for the above proposed system so that four fields of video signal is recorded for one track turn of the disc. This standard was set in order to increase the recording capacity under the restricting conditions introduced by the practical diameter and rotational speed of the disc, the relative linear speed between the reproducing stylus and the disc for obtaining a fine signal-to-noise (S/N) ratio, and the like.
When a still picture reproduction is performed with the above disc, the same track turn is reproduced repeatedly. Accordingly, the video signal of four fields is repeatedly reproduced in this case, to perform the still picture reproduction. However, especially when the movement in the picture which is to be reproduced is fast, the picture content in the first field of the video signal substantially differ from the picture content in the fourth field. Hence, a complete still picture cannot be obtained in this case, and the reproduced picture becomes unstable and unpleasant to watch.
In order to overcome the above described problems, a method may be considered in which the same video information content, that is, the content of the first field is recorded throughout the four fields in the one track turn. By this method, the content of the fifth field is recorded throughout the four fields in the succeeding track turn. Similarly, every fourth field is recorded throughout one track turn. In this case, even when the same track turn is repeatedly reproduced, the same field is repeatedly reproduced, and a complete and stable still picture can be obtained.
However, if a normal reproduction is performed with respect to the disc recorded in the above described manner, 3/4 of the picture information is dropped out, and the information content of the first, fifth, ninth, . . . fields are successively reproduced in units of four fields. Therefore, the movement in the picture which is reproduced becomes unstable and irregular.